Apparatus for keeping optimal penetration depth formed at front end of oxygen tuyere and method for keeping the same

ABSTRACT

An apparatus for keeping an optimal penetration depth formed at the front end of an oxygen tuyere in the producing facilities of molten pig iron utilizing non-coking coal and a method for keeping the same. A sensor for measuring distance using a laser for continuously measuring the penetration depth, is provided. Comprised is a process computer for continuously receiving the measured penetration depth from the sensor and comparing the received penetration depth with a predetermined optimal penetration depth to obtain a difference between them, and for obtaining a changing amount of a pressure in a melter gasifier through a mutual relation between a predetermined changing amount of a pressure in the melter gasifier with that of the penetration depth using the difference between the actual penetration depth with the optimal penetration depth. A scrubber cone controlling device for receiving the changing amount of the pressure in the melter gasifier from the process computer for changing an opening degree of a scrubber cone to change the pressure in the melter gasifier, is included. The apparatus and the method can actively cope with the change of the volumetric flow rate of the oxygen and the change of the constituting material in a coal packed bed, and can actively control an applied pressure in the melter gasifier to control the blowing velocity of the oxygen. The penetration depth can be optimally kept.

This application is a national stage of PCT/KR97/00273, filed Dec. 19,1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for keeping an optimalpenetration depth formed at the front end of an oxygen tuyere and amethod for keeping the same when producing molten pig iron utilizingnon-coking coal, and more particularly to an apparatus for keeping anoptimal penetration depth formed at the front end of an oxygen tuyereand a method for keeping the same using a sensor for measuring distancewhich is installed at the inside of oxygen tuyere when producing moltenpig iron utilizing non-coking coal.

2. Description of the Prior Art

Generally, a blast furnace method, which forms the majority of theproducing facilities of molten pig iron, requires raw material having astrength above a certain degree because of the characteristic of areactor. As a carbon source used as a fuel and a reducing agent, cokeobtained by processing a coking coal, is used. Accordingly, theproducing facilities of the coke should be necessarily accompanied. Inaddition, the exhaustion of the raw coal of the coke and the regulationof various environment contaminating materials generated during theproduction of the coke has rapidly decreased the competitive power ofthe blast furnace method.

To cope with the above-mentioned circumstance, world nations haveaccelerate the development of production method of molten pig iron,which utilize the non-coking coal as the fuel and the reducing agent.U.S. Pat. No. 4,978,387 discloses the conventional production facilitiesof the molten pig iron using the non-coking coal.

According to U.S. Pat. No. 4,978,387, energy required for variousprocesses is supplied through the combustion of a coal bed whileinjecting oxygen through a plurality of tuyeres, formed at the outerwall of the compacting layer with a constant distance in a circularshape, into the inner lower portion of the coal packed bed formed at amelter gasifier with a predetermined height. At this time, since thevolumetric flow rate and the pressure of the oxygen injected through thetuyere are quite large and intensive, a space formed toward the innerportion of the coal packed bed (i.e. a penetration depth) is inevitablyformed in front of the tuyere. The penetration depth largely affects theutilizing efficiency of the combustion energy, which is the supplysource of the required energy in the production facilities of the moltenpig iron utilizing the noncoking coal. Therefore, too short or too longpenetration depth forms the gas as an excessive circumferential flow oran excessive central flow in the coal packed bed to deteriorate theeffective use of the combustion energy.

Accordingly, an optimal keeping of the penetration depth is veryimportant in the operation of the production facilities of the moltenpig iron utilizing the non-coking coal. The optimal penetration depth iskept by keeping the oxygen blowing velocity at the tuyere constant bycontrolling the pressure applied in the melter gasifier according to thevolume of the oxygen blown through the tuyere, for the present.

However, the penetration depth formed in the coal packed bed is underthe influence of the structure, the particle size and the density of thecoal which forms the coal packed bed, as well as the oxygen blowingvelocity at the tuyere. Hence, even though the oxygen blowing velocityis kept constant, the optimal keeping of the penetration depth accordingto the change of various conditions of the raw material, is difficult.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to improve theproblems contained in the conventional method and to provide anapparatus for optimally keeping the penetration depth formed at thefront end of the oxygen tuyere and a method for optimally keeping thesame, which can actively cope with the change on the injection amount ofthe oxygen and the change on the constituting material in the coalpacked bed according to the change of various conditions of the rawmaterial and the operation.

To accomplish the object, there is provided in the present invention anapparatus for keeping an optimal penetration depth formed at a front endof an oxygen tuyere including a melter-gasifier for producing molten pigiron, a plurality of oxygen tuyeres formed around the outer lowerportion of the melter gasifier for blowing oxygen into the meltergasifier, a cyclone for receiving an exhausted gas from the meltergasifier and for separating powder from the exhausted gas, apre-reducing furnace for receiving the exhausted gas passed through thecyclone and for pre-reducing iron ores and a scrubber having a cone forcontrolling pressure in the melter gasifier, the apparatus comprising:

a sensor for measuring distance using a laser installed at an optionalone of the oxygen tuyeres for continuously measuring the penetrationdepth;

a process computer for continuously receiving the measured penetrationdepth from the sensor for measuring distance using a laser and comparingthe received penetration depth with a predetermined optimal penetrationdepth to obtain a difference between the actual penetration depth withthe optimal penetration depth, and for obtaining a changing amount ofpressure in the melter gasifier through a mutual relation between apredetermined changing amount of pressure in the melter gasifier with achanging amount of the penetration depth using the difference betweenthe actual penetration depth and the optimal penetration depth; and

a scrubber cone controlling device for receiving the changing amount ofthe pressure in the melter gasifier from the process computer and forchanging an opening degree of a scrubber cone to change the pressure inthe melter gasifier.

Another object of the present invention can be accomplished by a methodfor keeping an optimal penetration depth formed at a front end of anoxygen tuyere in a method for producing molten pig iron utilizing aproducing apparatus of the molten pig iron utilizing non-coking coal,the apparatus including a melter gasifier for producing molten pig iron,a plurality of oxygen tuyeres formed around the outer lower portion ofthe melter gasifier for blowing oxygen into the melter gasifier, acyclone for receiving an exhausted gas from the melter gasifier and forseparating powder from the exhausted gas, a pre-reducing furnace forreceiving the exhausted gas passed through the cyclone and forpre-reducing iron ores and a scrubber having a cone for controllingpressure in the melter gasifier, the method comprising the steps of:

establishing the optimal penetration depth according to a pressure inthe melter gasifier under a constant amount of oxygen blowing;

obtaining a mutual relation between a changing amount of a pressure inthe melter gasifier under a constant amount of oxygen blowing and achanging amount of the penetration depth;

continuously measuring the penetration depth by a sensor for measuringdistance using a laser installed at optional one of the oxygen tuyeres;

continuously obtaining a difference between the measured actualpenetration depth and the optimal penetration depth;

obtaining a changing amount of the pressure in the melter gasifier bythe mutual relation between the changing amount of the pressure in themelter gasifier and the changing amount of the penetration depthutilizing the difference between the measured actual penetration depthand the optimal penetration depth;

controlling the pressure in the melter gasifier as much as the changingamount of the obtained pressure by controlling an opening degree of thescrubber cone; and

repeating the steps until the actual penetration depth and the optimalpenetration depth become the same.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail preferred embodiments thereof withreference to the attached drawings in which:

FIG. 1 is a constituting diagram of an apparatus for keeping an optimalpenetration depth formed at the front end of an oxygen tuyere, which isprovided in the producing facilities of molten pig iron utilizingnoncoking coal, according to the present invention;

FIG. 2 is a detailed diagram of a sensor for measuring distance using alaser installed at the oxygen tuyere in the apparatus for keeping theoptimal penetration depth according to the present invention; and

FIG. 3 is a graph for showing the relation between the change of theblast volume of the oxygen and applied pressure in a melter gasifierwith respect to the change of the particle size of coal in a coal packedbed according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the preferred embodiment of the present invention will beexplained in more detail with reference to the accompanying drawings.

As illustrated in FIG. 1, the producing apparatus of the molten pig ironutilizing the non-coking coal includes a melter gasifier 11 formanufacturing the molten pig iron, a plurality of oxygen tuyeres 1formed around the outer lower wall of melter gasifier 11 for blowingoxygen into melter gasifier 11, a cyclone 12 for receiving exhausted gasfrom melter gasifier 11 and separating powder from the exhausted gas, apre-reducing furnace 13 for receiving the exhausted gas passed throughcyclone 12 and for pre-reducing iron ores and a scrubber 14 having acone 4 for controlling the pressure in melter gasifier 11.

The apparatus for keeping the optimal penetration depth formed at thefront end of the oxygen tuyere according to the present invention, isinstalled at one optional oxygen tuyere of the producing apparatus ofthe molten pig iron using the non-coking coal. The apparatus includes asensor for measuring distance using a laser 2 for continuously measuringa penetration depth la of the oxygen tuyere, a process computer 3 forobtaining the changing amount of an opening degree of the scrubber cone4 and a scrubber cone controlling device 7 for changing the openingdegree of scrubber cone 4.

Oxygen tuyeres 1 are formed at the lower and outer wall of a coal packedbed 11 a in melter gasifier 11 with a predetermined distance in aplurality of circular shapes. At the center portion of one optionaloxygen tuyere, sensor for measuring distance using a laser 2 formeasuring the penetration depth of the oxygen tuyere, is installed.

At the outer portion of sensor for measuring distance using laser 2, ahigh tension steel casing 21 is preferably installed to prevent amalfunction and a breakage due to the applied pressure in oxygen tuyere2, as illustrated in FIG. 2.

At the front end of high tension steel casing 21, a definite crevice 6is formed for transmitting the laser generated from sensor for measuringdistance using laser 2, and a fused silica having a plate shape 21 a anda predetermined thickness is inserted into the crevice.

Meanwhile, process computer 3 is connected with sensor for measuringdistance using a laser 2, as illustrated in FIG. 1, for continuouslyreceiving the measured actual penetration depth from sensor formeasuring distance using laser 2 and comparing the actual penetrationdepth with a predetermined optimal penetration depth to obtain adifference between the actual penetration depth and the optimalpenetration depth. Process computer 3 obtains the changing amount of thepressure in the melter gasifier by a mutual relation between thepredetermined changing amount of the pressure and the changing amount ofthe penetration depth in the melter gasifier utilizing the difference.

Scrubber cone controlling device 7 is connected with process computer 3and controls the pressure in melter gasifier 11 by changing the openingdegree of the scrubber cone by the changing amount of the pressure inmelter gasifier 11 obtained by process computer 4.

The blowing velocity of the oxygen through oxygen tuyere 1 can becontrolled through the controlling of the pressure in melter gasifier 11by changing the opening degree of scrubber cone 4 by means of scrubbercone controlling device 7. As the result, penetration depth la can beoptimally kept.

The method for keeping the optimal penetration depth formed at the frontend of the oxygen tuyere according to the present invention will beexplained, hereinafter.

In order to optimally keep the penetration depth formed at the front endof the oxygen tuyere according to the present invention, an optimalpenetration depth according to the pressure in the melter gasifier undera constant amount of the oxygen injection, should be established. Theoptimal penetration depth can be obtained through data from experimentsand experience.

In addition, the mutual relation between the changing amount of thepressure in the melter gasifier and the changing amount of thepenetration depth should be obtained in the present invention. Themutual relation can be obtained through data from experiments andexperience and also can be obtained by the following empirical equationsas in the present invention. For the conventional blast furnace, thefollowing empirical equation for the penetration depth formed at thefront end of the oxygen tuyere, is suggested.

L_(o)(penetration depth)=diameter of tuyere×(1.3744×10⁻²×RF+1.550)  (1)

RF(raceway factor)=(ρ_(go)·V_(o)²/g·S²)×(T_(b)P_(o)/T_(o)P)×(1/d_(so)·ρ_(so))  (1a)

(Wherein, V_(o): Volumetric flow rate of the oxygen

S: cross-sectional area of the tuyere

ρ_(go): gas density under a standard state

P: pressure in the furnace

T_(b): Oxygen temperature

P_(o), T_(o): pressure and temperature under a standard state(1atm,273K)

d_(so), ρ_(so): diameter and density of charging coke.)

The penetration depth formed at the front end of the oxygen tuyere inthe coal bed, has been presumed to use the above equation (1) in themethod for producing the molten pig iron using the production apparatusof the molten pig iron utilizing the non-coking coal. Accordingly, thepressure in the furnace obtained by equation (1) is selected as anoperating standard for keeping the optimal penetration depth.

However, equation (1) is the model equation which can be applied to thepacked bed consisting of coke which has homogeneous particle size anddensity and is stable to the reaction. Therefore, the direct applicationof equation (1) to the compacting layer consisting of the non-cokingcoal of which structure is largely changed by he kind of the coal, theoperating condition, etc. has a limitation.

That is, in the coal packed bed, the particle diameter and the densityat the front end of the tuyere are subjected to the influence of theconditions of the raw material and the operation of such as thecontained amount of the volatile material according to the kind of thecoal, the degree of the heat efficiency of the coal according to theincreasing velocity of the temperature and the pressure in the furnace,and the difference in the diameter decrease according to the reactivityfor the gasification, etc.

Accordingly, the utilization of the model equation for the realoperation is unreasonable.

A large change is formed in the distribution of the gas flow formed inthe coal packed bed of melter-gasifier due to the change of thepenetration depth in the melter gasifier, and this change affects thestability of the operation. Hence, the following model equation (2)which is obtained by improving equation (1) considering theabove-mentioned factors which affect the optimal penetration depth, isused in the present invention. Through equation (2), the optimalpenetration depth can be more rapidly obtained by obtaining the mutualrelation of the changing amount of the pressure in the melter gasifierand the changing amount of the penetration depth under a constant amountof the oxygen blowing.

La(penetration depth)=diameter of tuyere×a×RF +b  (2)

RF=(ρ_(go)·V_(o) ²/g·S²)×(T_(b)P_(o)/T_(o)P)×(1/d_(a)·ρ_(a))  (2a)

Wherein a and b are constants, d_(a) is the density of the coalcorresponding to 60-85% of the density of the coal before the charging(d_(so)) and ρ_(a) is the particle size of the coal corresponding to30-70% of the particle size of the coal before the charging (ρ_(so)).

That is, d_(a)=d_(so)×(0.6−0.85) and ρ_(a)=ρ_(so)×(0.3−0.7).

Of course, the mutual relation between the changing amount of thepressure in the melter gasifier and the changing amount of thepenetration depth under the constant amount of the oxygen blowing, canbe obtained considering the conventional operating data and experimentaldata, in the present invention.

Next, the penetration depth is continuously measured by installing thesensor for measuring distance using a laser at one optional oxygentuyere. The difference between the measured actual penetration depth andthe optimal penetration depth is continuously obtained.

The changing amount of the pressure in melter gasifier 11 is obtained bythe mutual relation of the changing amount of the pressure in meltergasifier 11 and the changing amount of the penetration depth using thedifference between the measured actual penetration depth and the optimalpenetration depth.

Next, the opening degree of the scrubber cone is controlled by thusobtained changing amount of the pressure to control the pressure inmelter gasifier 11. Then, the blowing velocity of the oxygen into theoxygen tuyere can be controlled and therefore, the penetration depth canbe controlled.

The optimal penetration depth formed at the front end of the oxygentuyere, can be kept by repeating the above-described steps until theactual penetration depth and the optimal penetration depth are the same.

Meanwhile, FIG. 3 is a graph illustrating the mutual relation betweenthe change of the blast volume of the oxygen blown through the oxygentuyere with the pressure applied in the melter gasifier for keeping theoptimal penetration depth (i.e. 0.6 m) formed at the front end of theoxygen tuyere, according to the particle sizes of the coal which formsthe coal packed bed. As illustrated in FIG. 3, the applied pressure inthe melter gasifier should be increased when the blast volume of theoxygen is increased to keep the optimal penetration depth. Further, theapplied pressure in the melter gasifier also should be increased whenthe particle size of the coal, which forms the coal compacting layer, issmaller.

As described above, the control of the optimal penetration depth formedat the front end of the oxygen tuyere can actively cope with the changeof the volumetric flow rate of the oxygen and the change of theconsisting material of the coal packed bed according to the change ofvarious conditions of raw material in the producing facilities of themolten pig iron utilizing the non-coking coal. Therefore, the utilizingefficiency of the coal combustion energy which is the main energysupplying source for the producing facilities of the molten pig ironutilizing the non-coking coal, can be maximized.

Although the preferred embodiment of the invention has been described,it is understood that the present invention should not be limited to thepreferred embodiment, but various changes and modifications can be madeby one skilled in the art within the spirit and scope of the inventionas hereinafter claimed.

What is claimed is:
 1. An apparatus for keeping an optimal penetrationdepth formed at a front end of an oxygen tuyere including a meltergasifier for producing molten pig iron, a plurality of oxygen tuyeresformed around the outer lower portion of said melter gasifier forblowing oxygen into said melter gasifier, a cyclone for receiving anexhausted gas from said melter gasifier and for separating powder fromsaid exhausted gas, a pre-reducing furnace for receiving said exhaustedgas passed through said cyclone and for pre-reducing iron ores and ascrubber having a cone for controlling pressure in said melter gasifier,said apparatus comprising: a sensor means including a laser formeasuring distance installed at one of said oxygen tuyeres forcontinuously measuring said penetration depth; a process computer forcontinuously receiving said measured penetration depth from said sensormeans and for comparing said received penetration depth with apredetermined optimal penetration depth to obtain a difference betweensaid actual penetration depth and said optimal penetration depth, andfor obtaining a changing amount of a pressure in said melter gasifierthrough a mutual relation between a predetermined changing amount of apressure in said melter gasifier and a changing amount of saidpenetration depth using said difference between said actual penetrationdepth and said optimal penetration depth; and a scrubber conecontrolling device for receiving said changing amount of said pressurein said melter gasifier from said process computer and for changing anopening degree of a scrubber cone to change said pressure in said meltergasifier.
 2. An apparatus for keeping an optimal penetration depthformed at a front end of an oxygen tuyere as claimed in claim 1, whereina high tension steel casing is provided at an outer portion of saidsensor for measuring distance using a laser and a constant crevice isformed at a front end of said casing.
 3. An apparatus for keeping anoptimal penetration depth formed at a front end of an oxygen tuyere asclaimed in claim 2, wherein a fused silica having a constant thicknessis inserted into said crevice formed at said front end of said casing.4. An apparatus for keeping an optimal penetration depth formed at afront end of an oxygen tuyere as claimed in claim 1, wherein a fusedsilica plate having a constant thickness is inserted into a creviceformed at a front end of a high tension steel casing.
 5. A method forkeeping an optimal penetration depth formed at a front end of an oxygentuyere in a method for producing molten pig iron utilizing a producingapparatus of said molten pig iron utilizing non-coking coal, saidapparatus including a melter gasifier for producing molten pig iron, aplurality of oxygen tuyeres formed around an outer lower portion of saidmelter gasifier for blowing oxygen into said melter gasifier, a cyclonefor receiving an exhausted gas from said melter gasifier and forseparating powder from said exhausted gas, a pre-reducing furnace forreceiving said exhausted gas passed through said cyclone and forpre-reducing iron ores and a scrubber having a cone for controllingpressure in said melter gasifier, said method comprising the steps of:(a) establishing said optimal penetration depth according to a pressurein said melter gasifier under a constant amount of oxygen blowing; (b)obtaining a mutual relation between a changing amount of a pressure insaid melter gasifier under a constant amount of oxygen blowing and achanging amount of said penetration depth; (c) continuously measuringsaid penetration depth by a sensor for measuring distance using a laserinstalled at one of said oxygen tuyeres; (d) continuously obtaining adifference between said measured actual penetration depth and saidoptimal penetration depth; (e) obtaining a changing amount of saidpressure in said melter gasifier by said mutual relation between saidchanging amount of said pressure in said melter gasifier and saidchanging amount of said penetration depth utilizing said differencebetween said measured actual penetration depth and said optimalpenetration depth; (f) controlling said pressure in said melter gasifieras much as said changing amount of said obtained pressure by controllingan opening degree of said scrubber cone; and (g) repeating steps (d),(e) and (f) until said actual penetration depth and said optimalpenetration depth become the same.
 6. A method for keeping an optimalpenetration depth formed at a front end of an oxygen tuyere as claimedin claim 5, wherein said mutual relation between said changing amount ofsaid pressure in said melter gasifier and said changing amount of saidpenetration depth under a constant amount of oxygen blowing is obtainedby the following equations: La (penetration depth)=diameter oftuyere×a×RF+b  Eq.2 and RF (raceway factor)=(ρ_(go)·V_(o)²/g·S²)×(T_(b)P_(o)/T_(o)P)×(1/d_(a)·ρ_(a))  Eq.2(a) wherein: a and bare constants, ρ_(go) is gas density under a standard state, V_(o) isvolumetric flow rate of the oxygen, g represents gravity constant, S isa cross-sectional area of the tuyere, T_(b) is oxygen temperature,P_(o), T_(o) are pressure and temperature under a standard state (1 atm,273K), P is pressure in the furnace, d_(a) is a density of coalcorresponding to 60-85% of a density of coal before charging (d_(so)),and ρ_(a) is a particle size of coal corresponding to 30-70% of aparticle size of coal before charging (ρ_(so)).